Hi everyone! I am still quite new with designing/making electronic systems and I am working on a watering system for our garden as my first big project. We have 7 raised beds we want to control the watering for each separately. The distance from where I plan to put the controller to the farthest bed is about 50 ft (15.5 m).
My current plan is to use a Pico W to control a relay for each solenoid valve and then run the wires to each valve at the bed in conduit. The solenoid valves I was looking at are 12V dc and draw about 0.42A. I dont anticipate having more than 2-3 valves open at once (due to limits of the water flow).
Here are my main questions:
Will i run into issues running all the wires in the same conduit (like interference when a valve is opened)? Is there any benefit of using a twisted pair vs single strands?
What gauge wire should I be using? I found a calculator that said i would need 22 awg for a distance of 50ft and a voltage drop of <10% (24 awg would be a 9.9% voltage drop so that seemed a little close).
Thanks for the help!
Hi Eric
Welcome
Depends on what you are using to switch the solenoids. If using relays there will be no issues at all. If using Mosfets the large spike at switch off could be a problem but a “flywheel diode” has to be fitted anyway with this type of switching so this will soak up any interfering spike.
In practice there could be. No need for twisting though. It makes it easier to identify the pairs of wires for wiring and any trouble shooting purposes. If it were me I would be using pairs.
Don’t forget the return wire which is in circuit so that 50’ will be actually 100’ of wire. Each solenoid requires 2 actual wires.
Cheers Bob
Hi @Eric289745
Welcome to the forum!
Being that data isn’t being transmitted and that it’s also quite low voltage there won’t really be any issue with interference.
The only real difference between using wire that is paired vs. single is that you will have to pull 1/2 as many lengths through the conduit if you use paired wires.
For the gauge of wire to use, 10% voltage drop is a fair bit and as @Robert93820 mentioned the distance is doubled as it will also need to make a return trip. I would recommend going a size or two larger than 22AWG for peace of mind.
Thank you so much for the quick reply! The calculator I found did say it takes the total loop length into account.
Hi all
That should not be any real problem as long as you use conduit that is large enough.
You should pull all the wires in at once anyway. Reason being that if you want to pull any in later there is a chance that friction CAN and WILL cut through the insulation on existing wires. For this reason if this is a permanent installation I would run a spare pair to each of the seven beds long enough to allow for future changes. Or at least put in a draw wire when installing operating wires. I would also used PVC sheathed pairs. Once again to assist in identifying pairs to each solenoid and also for some protection from any friction damage mentioned above.
During installation use a lubricant. There used to be a liquid (which I can’t remember the name of) specifically for that purpose. Alternatively French Chalk is good for this sort of thing. Very slippery, just dust it on lightly.
An alternative to conduit would be rectangular ducting with a lid. Could be easier as you can lay the wires in this without the need to pull anything with lubricant then put the lid on. What you use depends on circumstances, environment and your preference and really how much wiring protection you need. Conduit would be probably the best but just that bit more difficult.
Cheers Bob
